An Environmental Assessment of Soil State in the Impact Zone of the Sredneuralski Copper Smelter

Abstract

As part of the study of the ecological state of soils and vegetation in the zone of impact of the Sredneuralsky Copper Smelter (SNCS), the following tasks were solved: the content of heavy metals in the soils of the test sites laid within the zone of impact of the SNCS was determined; macrokinetic patterns of seasonal dynamics of the normalized relative vegetation index (NDVI) at the test sites in the zone of impact of the SNCS were revealed; macrokinetic patterns of vegetation response in the form of NDVI, calculated according to MODIS and Landsat 8 data, to soil pollution by a complex of heavy metals in the zone of impact of the SNCS were revealed; soil quality was ranked according to the patterns of vegetation response in the form of NDVI to soil pollution by a complex of heavy metals within the boundaries of the natural protection zone (NPZ) of the SNCS according to 2023. The intraseasonal dynamics of photosynthetically active biomass in the form of NDVI was modeled using a theoretical growth equation based on MODIS satellite data. The seasonal maximum of the vegetation index at the trial sites in 2012 fell on weeks 25‒28. In 2023, it occurred on weeks 27‒33, depending on the location of the sampling point. The rate of maximum achievement is characterized by weak intraseasonal and interannual variation. The patterns of changes in the concentration of photosynthetically active biomass in the form of maximum NDVI for the 2023 season in response to the gross content of a complex of heavy metals (Cu, Pb, Cd, and Zn) in the soil of the test sites were modeled using the theoretical equation of dose dependence. The maximum permissible level of the heavy-metal complex in the soil in the form of a geometric mean, which does not cause a decrease in the values of the vegetation index calculated according to the data of the MODIS and Landsat 8 satellites, was 101 and 106 mg kg^–1, respectively. An analysis of histograms of the distribution of NDVI values within the NPZ was carried out, which showed how the true frequencies of occurrence of the values of the vegetation index correspond to the empirical boundary of the NPZ associated with the maximum dose dependence point identified by the study of the 2012. The nature of the distribution of true NDVI values for the NPZ exclusively fully supports the used zoning theory based on the analysis of dose dependence. The modern boundaries of the SNCS natural protection zone are 4‒7 km away from the center of the sanitary protection zone.